Wim Huiskamp
SPI or I2C to UART Bridge
Dependents: SC16IS750_Test mbed_SC16IS750 Xadow_SC16IS750_Test Xadow_MPU9150AHRS
Diff: SC16IS750.cpp
- Revision:
- 2:76cb93b511f2
- Parent:
- 1:0440152c5387
- Child:
- 3:9783b6bde958
diff -r 0440152c5387 -r 76cb93b511f2 SC16IS750.cpp
--- a/SC16IS750.cpp Sun Feb 09 14:58:06 2014 +0000
+++ b/SC16IS750.cpp Thu Feb 13 17:12:02 2014 +0000
@@ -1,5 +1,5 @@
/* SC16IS750 interface
- * v0.1 WH, Nov 2013, Ported to mbed, Sparkfun Libs used as example. Added I2C and SPI I/F and more methods
+ * v0.1 WH, Nov 2013, Sparkfun Libs used as example. Added I2C I/F and many more methods.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of this software
* and associated documentation files (the "Software"), to deal in the Software without restriction,
@@ -19,6 +19,7 @@
#include "mbed.h"
#include "SC16IS750.h"
+#define ENABLE_BULK_TRANSFERS 0x01
/** Abstract class SC16IS750 for converter between either SPI or I2C and a Serial port
* Constructor for this Abstract Class is protected
@@ -40,7 +41,7 @@
* @return none
*/
void SC16IS750::baud(int baudrate) {
- unsigned long divisor = BAUD_RATE_DIVISOR(baudrate);
+ unsigned long divisor = SC16IS750_BAUDRATE_DIVISOR(baudrate);
char lcr_tmp;
_config.baudrate = baudrate; // Save baudrate
@@ -58,6 +59,7 @@
* @param bits The number of bits in a word (5-8; default = 8)
* @param parity The parity used (Serial::None, Serial::Odd, Serial::Even, Serial::Forced1, Serial::Forced0; default = Serial::None)
* @param stop_bits The number of stop bits (1 or 2; default = 1)
+ * @return none
*/
void SC16IS750::format(int bits, Serial::Parity parity, int stop_bits) {
char lcr_tmp = 0x00;
@@ -103,6 +105,7 @@
};
/** Generate a break condition on the serial line
+ * @return none
*/
void SC16IS750::send_break() {
// Wait for 1.5 frames before clearing the break condition
@@ -120,6 +123,7 @@
/** Set a break condition on the serial line
* @param enable break condition
+ * @return none
*/
void SC16IS750::set_break(bool enable) {
@@ -136,10 +140,12 @@
/** Set the flow control type on the serial port
* Added for compatibility with Serial Class.
* SC16IS750 supports only Flow, Pins can not be selected.
+ * This method sets only hardware flow control. SC16IS750 supports XON/XOFF, but this is not implemented.
*
* @param type the flow control type (Disabled, RTS, CTS, RTSCTS)
- * @param flow1 the first flow control pin (RTS for RTS or RTSCTS, CTS for CTS)
- * @param flow2 the second flow control pin (CTS for RTSCTS)
+ * @param flow1 the first flow control pin (RTS for RTS or RTSCTS, CTS for CTS) - NOT USED
+ * @param flow2 the second flow control pin (CTS for RTSCTS) - NOT USED
+ * @return none
*/
void SC16IS750::set_flow_control(Flow type, PinName flow1, PinName flow2) {
char lcr_tmp;
@@ -161,15 +167,55 @@
}
- //Save flowcontrol state
- //enable enhanced functions
- _config.flowctrl = efr_tmp | EFR_ENABLE_ENHANCED_FUNCTIONS,
+ //Save flowcontrol mode and enable enhanced functions
+ _config.flowctrl = efr_tmp | EFR_ENABLE_ENHANCED_FUNCTIONS;
lcr_tmp = this->readRegister(LCR); // save LRC register
this->writeRegister(LCR, LCR_ENABLE_ENHANCED_FUNCTIONS); // write magic number 0xBF to enable access to EFR register
this->writeRegister(EFR, _config.flowctrl); // set flow and enable enhanced functions
this->writeRegister(LCR, lcr_tmp); // restore LCR register
}
+
+/** Set the RX FIFO flow control levels
+ * This method sets only hardware flow control levels. SC16IS750 supports XON/XOFF, but this is not implemented.
+ * Should be called BEFORE Auto RTS is enabled.
+ *
+ * @param resume trigger level to resume transmission (0..15, meaning 0-60 with a granularity of 4)
+ * @param halt trigger level to resume transmission (0..15, meaning 0-60 with granularity of 4)
+ * @return none
+ */
+void SC16IS750::set_flow_triggers(int resume, int halt) {
+
+ // sanity checks
+ halt = halt & 0x0F;
+ resume = resume & 0x0F;
+ if (halt <= resume) {
+ halt = TCR_HALT_DEFAULT;
+ resume = TCR_RESUME_DEFAULT;
+ }
+
+ // Note: TCR accessible only when EFR[4]=1 and MCR[2]=1
+ this->writeRegister(TCR, (resume << 4) | halt); // set TCR register
+}
+
+
+/** Set the Modem Control register
+ * This method sets prescaler, enables TCR and TLR
+ *
+ * @param none
+ * @return none
+ */
+void SC16IS750::set_modem_control() {
+
+ //Note MCR[7:4] and MCR[2] only accessible when EFR[4] is set
+ if (SC16IS750_PRESCALER == SC16IS750_PRESCALER_1) { // Default prescaler after reset
+ this->writeRegister(MCR, MCR_PRESCALE_1 | MCR_ENABLE_TCR_TLR);
+ }
+ else {
+ this->writeRegister(MCR, MCR_PRESCALE_4 | MCR_ENABLE_TCR_TLR);
+ }
+}
+
/** Initialise internal registers
@@ -184,29 +230,40 @@
// Software reset, assuming there is no access to the HW Reset pin
swReset();
-
- // Set default baudrate and save in _config
- // LCR, DLL/DLH
+
+ // Set default baudrate (depends on prescaler) and save in _config
+ // DLL/DLH
baud();
- // Set dataflow and save in _config
- // LCR, EFR
- set_flow_control();
-
// Set default dataformat and save in _config
// LCR
format();
+ // Set dataflow mode and Enables enhanced functions
+ // Save in _config
+ // EFR
+ set_flow_control();
+
+
+ // FIFO control, sets TX and RX trigger levels and enables FIFO and save in _config
+ // Note FCR[5:4] only accessible when EFR[4] is set (enhanced functions enable)
+ // FCR, TLR
+ set_fifo_control();
+ flush();
+
+ // Modem control, sets prescaler, enable TCR and TLR
+ // Note MCR[7:4] and MCR[2] only accessible when EFR[4] is set (enhanced functions enable)
+ set_modem_control();
+
+ // Set RTS trigger levels
+ // Note TCR only accessible when EFR[4] is set (enhanced functions enable) and MCR[2] is set
+ set_flow_triggers();
+
+
// Set default break condition and save in _config
// LCR
//set_break();
-
- // Set default fifoformat and save in _config
- // FCR
- _config.fifoenable = true;
- _config.fifoformat = FCR_RX_IRQ_NONE | FCR_ENA_FIFO_64;
- flush();
-
+
// The UART bridge should now be successfully initialised.
// Test if UART bridge is present and initialised
@@ -224,12 +281,48 @@
}
+
+/** FIFO control, sets TX and RX trigger levels and enables FIFO and save in _config
+ * Note FCR[5:4] (=TX_IRQ_LVL) only accessible when EFR[4] is set (enhanced functions enable)
+ * Note TLR only accessible when EFR[4] is set (enhanced functions enable) and MCR[2] is set
+ * @param none
+ * @return none
+ */
+void SC16IS750::set_fifo_control() {
+
+ // Set default fifoformat
+ // FCR
+ _config.fifoenable = true;
+
+ // Note FCR[5:4] (=TX_IRQ_LVL) only accessible when EFR[4] is set (enhanced functions enable)
+// _config.fifoformat = FCR_RX_IRQ_8 | FCR_TX_IRQ_56;
+ _config.fifoformat = FCR_RX_IRQ_8 | FCR_TX_IRQ_8; //Default
+
+ if (_config.fifoenable)
+ // enable FIFO mode and set FIFO control values
+ this->writeRegister(FCR, _config.fifoformat | FCR_ENABLE_FIFO);
+ else
+ // disable FIFO mode and set FIFO control values
+ this->writeRegister(FCR, _config.fifoformat);
+
+ // Set Trigger level register TLR for RX and TX interrupt generation
+ // Note TLR only accessible when EFR[4] is set (enhanced functions enable) and MCR[2] is set
+ // TRL Trigger levels for RX and TX are 0..15, meaning 0-60 with a granularity of 4 chars
+ // When TLR for RX or TX are 'Zero' the corresponding values in FCR are used. The FCR settings
+ // have less resolution (only 4 levels) so TLR is considered an enhanced function.
+ this->writeRegister(TLR, 0x00); // Use FCR Levels
+// this->writeRegister(TLR, (TLR_RX_DEFAULT << 4) | TLR_TX_DEFAULT); // Use Default enhanced levels
+
+}
+
+
/**
* Flush the UART FIFOs while maintaining current FIFO mode.
* @param none
* @return none
*/
void SC16IS750::flush() {
+ // FCR is Write Only, use saved _config
// reset TXFIFO, reset RXFIFO, non FIFO mode
this->writeRegister(FCR, FCR_TXFIFO_RST | FCR_RXFIFO_RST);
@@ -277,22 +370,30 @@
/** Determine if there is a character available to read.
+ * This is data that's already arrived and stored in the receive
+ * buffer (which holds 64 chars).
+ *
* @return 1 if there is a character available to read, 0 otherwise
*/
int SC16IS750::readable() {
- return (this->readRegister(LSR) & 0x01);
+
+// if (this->readableCount() > 0) { // Check count
+ if (this->readRegister(LSR) & LSR_DR) { // Data in Receiver Bit, at least one character waiting
+ return 1;
+ }
+ else {
+ return 0;
+ }
+
}
/** Determine how many characters are available to read.
+ * This is data that's already arrived and stored in the receive
+ * buffer (which holds 64 chars).
+ *
* @return int Characters available to read
*/
int SC16IS750::readableCount() {
- /*
- * Get the number of chars (characters) available for reading.
- *
- * This is data that's already arrived and stored in the receive
- * buffer (which holds 64 chars).
- */
return (this->readRegister(RXLVL));
}
@@ -301,22 +402,25 @@
* @return 1 if there is a space for a character to write, 0 otherwise
*/
int SC16IS750::writable() {
- return (this->writableCount() > 0); // Check datasheet for faster version
+
+// if ((this->writableCount() > 0) { // Check count
+ if (this->readRegister(LSR) & LSR_THRE) { // THR Empty, space for at least one character
+ return 1;
+ }
+ else {
+ return 0;
+ }
}
/** Determine how much space available for writing characters.
+ * This considers data that's already stored in the transmit
+ * buffer (which holds 64 chars).
+ *
* @return int character space available to write
*/
int SC16IS750::writableCount() {
- /*
- * Get the available space for writing characters.
- *
- * This is data that's already stored in the transmit
- * buffer (which holds 64 chars).
- */
- return (this->readRegister(TXLVL));
-// return (readRegister(64 - TXLVL)); //Check datasheet
+ return (this->readRegister(TXLVL)); // TX Level
}
@@ -341,6 +445,7 @@
* @return value written
*/
int SC16IS750::putc(int value) {
+
while (this->readRegister(TXLVL) == 0) {
// Wait for space in TX buffer
wait_us(10);
@@ -350,39 +455,62 @@
return value;
}
-
+/**
+ * Write char string to UART Bridge. Blocking when no free space in FIFO
+ * @param *str char string to be written
+ * @return none
+ */
void SC16IS750::write(const char *str) {
- /*
- * Write string to UART.
- */
- write((const uint8_t *) str, strlen(str));
- while (this->readRegister(TXLVL) < 64) {
- // Wait for empty TX buffer (slow)
- wait_us(10);
- // (But apparently still not slow enough to ensure delivery.)
- };
-}
#if ENABLE_BULK_TRANSFERS
-void SC16IS750::write(const uint8_t *buffer, size_t size) {
- /*
+
+ #define BULK_BLOCK_LEN 16
+ int len, idx;
- Write buffer to UART.
-
- */
- //select();
- //transfer(THR); // TODO: Change this when we modify register addresses? (Even though it's 0x00.)
+ len = strlen(str);
- while(size > 16) {
- //transfer_bulk(buffer, 16); //ringbuffer?
- size -= 16;
- buffer += 16;
+ // Write blocks of BULK_BLOCK_LEN
+ while (len > BULK_BLOCK_LEN) {
+ while(this->readRegister(TXLVL) < BULK_BLOCK_LEN) {
+ // Wait for space in TX buffer
+ wait_us(10);
+ };
+
+ // Write a block of BULK_BLOCK_LEN bytes
+ // Note: can be optimized by writing registeraddress once and then repeatedsly write the bytes.
+ for (idx=0; idx<BULK_BLOCK_LEN; idx++) {
+ this->writeRegister(THR, str[idx]);
+ };
+
+ len -= BULK_BLOCK_LEN;
+ str += BULK_BLOCK_LEN;
}
- //transfer_bulk(buffer, size);
+
+ // Write remaining bytes
+ for (idx=0; idx<len; idx++) {
+ while (this->readRegister(TXLVL) == 0) {
+ // Wait for space in TX buffer
+ wait_us(10);
+ };
+ this->writeRegister(THR, str[idx]);
+ }
+
- //deselect();
+#else
+ int len, idx;
+
+ len = strlen(str);
+ for (idx=0; idx<len; idx++) {
+ while (this->readRegister(TXLVL) == 0) {
+ // Wait for space in TX buffer
+ wait_us(10);
+ };
+ this->writeRegister(THR, str[idx]);
+ }
+#endif
}
-#endif
+
+
/** Set direction of I/O port pins.
* This method is specific to the SPI-I2C UART and not found on the 16750
SC16IS750 and SC16IS752 I2C or SPI to UART bridge